Peel and finely mince the onion and garlic. In a small skillet heat 1 tablespoon olive oil over medium heat and gently sweat the minced onion with a pinch of salt until translucent, about 5 minutes. Add the minced garlic and cook 30–45 seconds until fragrant. Remove from heat and let cool slightly.

Soak breadcrumbs

Place the breadcrumbs in a small bowl and pour in the milk. Stir and let sit 5 minutes until breadcrumbs absorb the milk and become a thick paste.

Combine meatball mixture

In a large mixing bowl combine ground beef and ground pork. Add the soaked breadcrumbs, cooled onion-garlic mixture, grated Parmesan, chopped parsley, eggs, dried oregano, salt and pepper. Using your hands or a sturdy spoon, gently mix until just combined — avoid overworking the meat to keep meatballs tender.

Portion meatballs

For a 25-piece pan, portion about 2 ounces (roughly golf-ball size) per meatball. Using a scale or tablespoon, portion 25 equal portions and gently roll each between your palms into a smooth ball. Place formed meatballs on a rimmed baking sheet or platter.

Brown meatballs

Heat a large ovenproof skillet (or two pans as needed) over medium-high heat and add remaining 2 tablespoons olive oil. Working in batches so you don't overcrowd the pan, add meatballs and brown on all sides, turning gently with tongs or a spatula, about 2–3 minutes per side. Transfer browned meatballs to a plate while you brown remaining batches.

Finish cooking (oven method)

Preheat oven to 375°F (190°C). Return all browned meatballs to the skillet in a single layer. Place the skillet in the preheated oven and bake until cooked through (internal temperature 160°F/71°C), about 12–15 minutes depending on size. Remove from oven and let rest 5 minutes before serving.

Finish cooking (sauce method)

Alternatively, after browning, pour warmed tomato sauce (see next section) into the skillet to cover the bottom, nestle meatballs into the sauce, bring to a gentle simmer on the stove, then cover and simmer 15–20 minutes until cooked through. This yields saucier meatballs.

Simple Tomato Sauce (optional, for serving)

In a medium saucepan heat 1 tablespoon olive oil over medium heat. Add the minced garlic and cook 30–45 seconds until fragrant but not browned. Pour in the crushed tomatoes, add salt, pepper, dried basil and sugar if using. Stir to combine and bring to a low simmer. Reduce heat to low and simmer uncovered 10–15 minutes to meld flavors, stirring occasionally. Taste and adjust seasoning.

If using the sauce with browned meatballs, either nestle meatballs into the sauce and simmer covered 15–20 minutes until cooked through, or pour sauce over baked meatballs before serving.